The man, identified only as Rajat, pleaded guilty on Wednesday to one charge of using criminal force with the intent to outrage modesty, according to The Straits Times.
The incident occurred in late February during a flight from Perth, Australia, to Singapore. While the flight attendant was cleaning a restroom, Rajat approached her and placed both hands on her hips near her buttocks, Channel News Asia reported.
A female passenger who witnessed the act quickly intervened, pulling the attendant out of the restroom and escorting her to the back of the plane.
Rajat was arrested upon arrival at Changi Airport.
Under Singaporean law, those convicted of molestation can face up to three years in prison, a fine, caning, or a combination of these penalties.